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On board generator
- Thread starter longshadows
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I knew that much - it’s something they added to the rules for racing a few years back - but that article covers a bunch of systems from different vendors that function in very different ways.
So what I was really asking was which of the various kers systems he was referring to, though I may not have been clear about my question.
My guess was he meant whatever Tesla was using, which is why I went on with that, even though it isn’t exactly a kers system.
I was not familiar with the KERS acronym either but note that the Tesla system recovers potential (gravitational) energy too. It is this that has given me W/mi of 160 on one trip and even -146 on one notable occasion.
It is critical that people understand the the "motors" used in the Tesla cars are symmetrical 4 quadrant machines which means that they can produce or absorb torque when running in either direction. What they do is determined by the current that flows in the stator windings and that is controlled by a set of 6 switches which are turned on and off in the proper order, at the proper speed and at the proper duty cycle to effect the desired torque result. I should also state clearly here that I have never seen any Tesla documentation supporting this description. It assumes that Tesla is using modern 3 phase motor control techniques and the evidence certainly seems to support this. Assuming this description to be reasonably accurate then the design would capture nearly all the energy that is available to be captured. That which has been lost to heating of the air, the tyres, the road bed, the inverter/rectifier and potential energy is not recoverable (except for the potential when you go back down the hill). The generator is not 100% efficient so there will be some losses there but Tesla has done an excellent job of tweaking. The SWPMMs, for example, eliminate rotor I^2R and hysteresis losses. The inverter/rectifier (the 6 switches) isn't 100% efficient either. Some heat is dissipated during the transition from on to off. There may be some room for improvement there (by developing transistors that can switch faster for example) but they are working well above 90% and there just isn't that much more efficiency to be garnered. But every little bit does count and I am sure Tesla and the other manufacturers are looking at ways to get even a fraction of a percent more efficiency. At the same time an improvement in overall efficiency of the vehicle of 1% only implies about 3 miles extra range and as improvement in the regen system to 100% would not give even that 1% overall it isn't likely that any regen scheme is going to give a notable improvement over what is available now.
It is critical that people understand the the "motors" used in the Tesla cars are symmetrical 4 quadrant machines which means that they can produce or absorb torque when running in either direction. What they do is determined by the current that flows in the stator windings and that is controlled by a set of 6 switches which are turned on and off in the proper order, at the proper speed and at the proper duty cycle to effect the desired torque result. I should also state clearly here that I have never seen any Tesla documentation supporting this description. It assumes that Tesla is using modern 3 phase motor control techniques and the evidence certainly seems to support this. Assuming this description to be reasonably accurate then the design would capture nearly all the energy that is available to be captured. That which has been lost to heating of the air, the tyres, the road bed, the inverter/rectifier and potential energy is not recoverable (except for the potential when you go back down the hill). The generator is not 100% efficient so there will be some losses there but Tesla has done an excellent job of tweaking. The SWPMMs, for example, eliminate rotor I^2R and hysteresis losses. The inverter/rectifier (the 6 switches) isn't 100% efficient either. Some heat is dissipated during the transition from on to off. There may be some room for improvement there (by developing transistors that can switch faster for example) but they are working well above 90% and there just isn't that much more efficiency to be garnered. But every little bit does count and I am sure Tesla and the other manufacturers are looking at ways to get even a fraction of a percent more efficiency. At the same time an improvement in overall efficiency of the vehicle of 1% only implies about 3 miles extra range and as improvement in the regen system to 100% would not give even that 1% overall it isn't likely that any regen scheme is going to give a notable improvement over what is available now.
The Tesla system, as hypothesized, sends the energy directly back to the battery. Small capacitors (pF) would be used to absorb switching transients. But not the supercapacitors which are 15 orders of magnitude larger.
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I'm not sure what you are trying to say here as you post a screen shot showing -1100 Wh/mi. Nor am I sure why the post was rated funny. Negative consumption is perfectly valid (though the 999 miles range that is displayed with it isn't). An average negative consumption of -1000 over 5 miles indicates that the average grade was about -10%.
I guess I needed more emoticons in my post.
I wasn’t disputing anything you said about regen or negative consumption - quite the contrary.
I thought showing the extreme case had the potential to be funny presented the right way, and clearly one person got my sense of humor, but apparently you didn’t.
And yes, I think Mt Washington Auto Road may be the steepest paved road of that sort of length in the US (though there’s actually a mile of gravel most of the way up.)
Pike’s Peak and Mt Evans in Colorado are of course higher, and both have more total altitude gain, but it’s over a longer distance.
I was surprised at how consistent the grade is on the Auto Road, actually. It was no challenge at all to the Tesla going up or down, which I doubt surprises anyone. The only place I needed the brakes was when the guy in front of me messed up a passing zone and jammed his on at the last minute.
HankLloydRight
No Roads
But I don’t need anyone to hold my beer. I have several nice cup holders and Autopilot.
It has been a couple weeks.
Regenerative braking. We already have this.
I want to be very careful to not be insulting here. But learning about energy recovery from any system is, and again I'm being honest and not insulting in any way, grade school science. We learned about these things in primary school in the 80s, and education has come a looooooong way since then. The physics of this kind of stuff goes back to the laws of thermodynamics. Descriptions of observations from the late 1700s through the 1800s.
This is all to say that these phenomenon are very well understood, very well studied, and that the saying "There's no free lunch" is as true now as it has ever been. The tires of these vehicles make direct contact with the ground, and they have the force of the vehicle weighing them down. Their ability to transfer energy into or out of the vehicle surpasses the passengers' ability to be comfortable and keep their stomach contents where they belong. Using the existing electric motors allows Tesla to use them for two purposes, doubling their value in the car. They propel the car _and_ they turn into multi-phase A/C electric generators when the car is moving faster than the motors are propelling it.
There is no system you're going to invent as a non-engineer that is going to surpass the literal centuries of research and discovery involved here. Let alone Tesla's half-decade of work on squeezing efficiency from the drive system.
I am in the application stage for patent pending.
No insult taken. I guess I didn't pay much attention in class in my youth.
I am not inventing a system. I am just trying to add a piece to the puzzle that I think is missing and hope that it fits.
I have to see it through until I am told hell no.
Find an EE. Have him sign an NDA and show him what you have in mind. The odds are 99.99999% that you have nothing and him shutting you down now may save you some money. OTOH there is that !e-6% chance that you have come up with a new twist.Viable ones would be something like a new electrolyte additive for the batteries or a new dopant for FETs that makes them switch faster.
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